Unit 2 Study Guide: Integumentary, Skeletal, and Articular Systems

Integumentary System

Vocabulary

• Epidermis: The outermost layer of the skin, composed primarily of stratified squamous epithelial tissue. It provides a protective barrier against environmental damage.

• Dermis: The middle layer of the skin, made of connective tissue, containing blood vessels, nerves, hair follicles, and glands.

• Hypodermis (Subcutaneous Layer): The deepest layer, consisting mainly of adipose (fat) tissue, which insulates and cushions the body.

• Arrector Pili Muscle: Small muscles attached to hair follicles; contraction causes 'goosebumps.'

• Melanin: A pigment produced by melanocytes that gives skin its color and protects against UV radiation.

• Keratin: A tough, fibrous protein in the epidermis that provides strength and waterproofing.

Functions of the Skin

• Protection from mechanical, chemical, and biological damage

• Prevents water loss

• Regulates body temperature

• Sensory reception (touch, pain, temperature)

• Vitamin D synthesis

• Excretion of wastes through sweat

Skin Cancers

• Most common: Basal cell carcinoma

• Most deadly: Melanoma

Epidermis

• Type of tissue: Keratinized stratified squamous epithelium

• Layers (from superficial to deep):

  1. Stratum corneum: Dead, keratinized cells; provides protection

  2. Stratum lucidum: Present only in thick skin (palms, soles)

  3. Stratum granulosum: Cells begin to die; keratinization starts

  4. Stratum spinosum: Several layers of keratinocytes; provides strength

  5. Stratum basale: Deepest layer; site of cell division and melanocytes

• Nutrient source: Diffusion from blood vessels in the dermis

• Role of keratin: Provides waterproofing and mechanical strength

• Skin color differences: All people have a similar number of melanocytes; darker skin results from increased melanin production, not more melanocytes.

Dermis

• Layers:

  • Papillary layer: Superficial, areolar connective tissue, forms dermal papillae

  • Reticular layer: Deep, dense irregular connective tissue, provides strength and elasticity

• Hair:

  • Parts of hair: Shaft (above skin), root (below skin), bulb (base of follicle)

  • Parts of follicle: Inner and outer root sheaths, hair matrix (growth region)

Glands

• Merocrine (Eccrine) glands: Secrete watery sweat for thermoregulation; found all over the body

• Apocrine glands: Found in axillary and genital areas; secrete thicker sweat; responsible for body odor after puberty

• Sebaceous glands: Secrete sebum (oil) into hair follicles; lubricates skin and hair

• Ceruminous glands: Modified sweat glands in the ear canal; produce earwax

Nails

• Parts:

  • Matrix: Growth region at the nail base

  • Lunula: Whitish, crescent-shaped area at the base

  • Nail bed: Skin beneath the nail plate

  • Free edge: Part of the nail that extends beyond the finger

Skin and Temperature Homeostasis

• Response to cold: Vasoconstriction, shivering, contraction of arrector pili muscles

• Response to heat: Vasodilation, increased sweat production

Burns

• 1st degree: Only epidermis affected; redness, pain

• 2nd degree: Epidermis and part of dermis; blisters, pain

• 3rd degree: Full thickness; destroys epidermis and dermis; may appear white or charred, often painless due to nerve damage

Skeletal System

Vocabulary

• Bursa: Fluid-filled sac that reduces friction between tissues

• Tendon: Connects muscle to bone

• Ligament: Connects bone to bone

Functions of the Skeletal System

• Support

• Protection of internal organs

• Movement (leverage for muscles)

• Mineral storage (especially calcium and phosphate)

• Blood cell production (hematopoiesis in red marrow)

• Triglyceride storage (yellow marrow)

Cartilage

• Cells:

  • Chondroblasts: Produce new cartilage matrix

  • Chondrocytes: Mature cartilage cells, maintain matrix

• Perichondrium: Dense connective tissue surrounding cartilage; contains blood vessels for nutrient delivery

• Type associated with bone growth: Hyaline cartilage

• Growth types:

  • Appositional: Growth at the surface (new layers added)

  • Interstitial: Growth from within (chondrocytes divide and secrete matrix)

Bone

• Rickets: Disease in children caused by vitamin D deficiency, leading to soft, weak bones

• Main mineral: Calcium phosphate (as hydroxyapatite crystals)

• Cell types:

  • Osteoblast: Bone-forming cell

  • Osteocyte: Mature bone cell, maintains bone tissue

  • Osteoclast: Bone-resorbing cell

  • Stem cell: Osteoprogenitor cell (also gives rise to chondroblasts)

• Spongy bone: Porous, contains trabeculae; houses red marrow (site of hematopoiesis) and yellow marrow (fat storage)

• Compact bone: Dense, organized into osteons (Haversian systems)

  • Lamellae: Concentric (around osteons), circumferential (around bone), interstitial (between osteons)

  • Lacunae: Small spaces housing osteocytes

• Periosteum: Outer fibrous covering of bone; contains nerves and blood vessels

• Endosteum: Thin membrane lining the medullary cavity

Shapes of Bones

• Long bones: Longer than wide (e.g., femur, humerus)

• Flat bones: Thin, flattened (e.g., sternum, skull bones)

• Irregular bones: Complex shapes (e.g., vertebrae)

• Short bones: Cube-shaped (e.g., carpals, tarsals)

• Parts of a long bone: Diaphysis (shaft), epiphysis (ends), metaphysis (between shaft and end), medullary cavity (marrow cavity)

Fractures

• Types include simple (closed), compound (open), comminuted, greenstick, spiral, and others

Bone Growth

• Intramembranous ossification: Bone develops from fibrous membrane (e.g., flat bones of skull)

• Endochondral ossification: Bone forms by replacing hyaline cartilage (e.g., long bones)

Axial and Appendicular Skeleton

Vocabulary

• Tubercle: Small rounded projection on a bone

• Foramen: Opening or hole in a bone for passage of nerves/vessels

• Sinus: Air-filled cavity within a bone

• Body (of a bone): Main portion of a bone

• Tuberosity: Large, rough projection

• Spine (of a bone): Sharp, slender projection

• Condyle: Rounded articular projection

• Meatus: Canal-like passageway

• Scoliosis: Lateral curvature of the spine

• Kyphosis: Exaggerated thoracic curvature (humpback)

• Lordosis: Exaggerated lumbar curvature (swayback)

Bones of the Axial Skeleton

• Includes skull, vertebral column, and thoracic cage

• Skull:

  • Paired bones: Parietal, temporal, maxilla, zygomatic, nasal, lacrimal, palatine, inferior nasal concha

  • Unpaired bones: Frontal, occipital, sphenoid, ethmoid, mandible, vomer

  • Examples:

    • Roof of orbits and bony eyebrows: Frontal bone

    • Cheekbones: Zygomatic bones

    • Upper jaw: Maxilla

    • Lower jaw: Mandible

  • Sutures: Coronal (frontal/parietal), sagittal (between parietals), lambdoid (parietal/occipital), squamous (parietal/temporal)

  • Nasal septum: Formed by vomer and perpendicular plate of ethmoid

  • Sinuses: Frontal, maxillary, sphenoid, ethmoid bones

  • Foramen magnum: Passage for spinal cord (in occipital bone)

  • Special sense organ in orbit: Eye

Bones of the Appendicular Skeleton

• Scapula: Shoulder blade; located on posterior thorax

• Upper limb:

  • Arm: Humerus

  • Forearm: Radius (lateral in anatomical position), ulna (medial)

  • Wrist: Carpals (8 bones)

  • Hand: Metacarpals (5 bones)

  • Fingers: Phalanges (14 bones)

• Lower extremity:

  • Bone you sit on: Ischial tuberosity (part of ischium)

  • Tibia (medial, has medial malleolus), fibula (lateral, has lateral malleolus)

  • Tarsal bone articulating with tibia/fibula: Talus

Regions of the Spine

• Cervical (7), thoracic (12), lumbar (5), sacrum (5 fused), coccyx (4 fused)

• Coccyx: Tailbone, at base of spine

• 1st cervical vertebra: Atlas

• 2nd cervical vertebra: Axis

Thoracic Cage

• Sternum: Manubrium, body, xiphoid process

• Ribs:

  • True ribs (1-7): Attach directly to sternum

  • False ribs (8-12): Attach indirectly or not at all

  • Floating ribs (11-12): No anterior attachment

Joints (Articulations)

Vocabulary

• Fibrous joint: Bones joined by dense connective tissue; little or no movement (e.g., sutures)

• Cartilaginous joint: Bones joined by cartilage (e.g., symphysis, synchondrosis)

• Symphysis: Joint where bones are joined by fibrocartilage (e.g., pubic symphysis)

• Syndesmosis: Joint where bones are connected by a ligament (e.g., distal tibiofibular joint)

• Synostosis: Fusion of two bones into one (e.g., epiphyseal line)

• Suture: Immovable joint between skull bones

• Gomphosis: Peg-in-socket joint (e.g., teeth in sockets)

• Bursa: Fluid-filled sac reducing friction

• Plane joint: Flat surfaces; gliding movement (e.g., intercarpal joints)

• Hinge joint: Movement in one plane (e.g., elbow)

• Ball-and-socket joint: Multiaxial movement (e.g., shoulder, hip)

• Pivot joint: Rotation around a single axis (e.g., atlas/axis)

• Saddle joint: Biaxial movement (e.g., thumb)

• Ellipsoid joint: Biaxial movement (e.g., wrist)

Structural Classifications of Joints

• Fibrous: Sutures, syndesmoses, gomphoses; immovable or slightly movable

• Cartilaginous: Synchondroses (hyaline cartilage), symphyses (fibrocartilage); slightly movable

• Synovial: Most joints in appendicular skeleton; freely movable; have joint cavity, synovial fluid, articular cartilage, joint capsule

Synovial Joints

• Synovial fluid: Lubricates, nourishes cartilage, absorbs shock

• Joint capsule: Fibrous outer layer and inner synovial membrane

• Elbow joint: Hinge joint (uniaxial movement)

• Rotator cuff muscles: Associated with shoulder (glenohumeral) joint

• Labrum: Cartilaginous ring in shoulder and hip joints

• Knee ligaments:

  • ACL (anterior cruciate ligament): Prevents anterior movement of tibia

  • PCL (posterior cruciate ligament): Prevents posterior movement of tibia

• Arches of the foot: Absorb shock, distribute weight

• Aging: Joints become stiffer, cartilage wears down, risk of arthritis increases

Movements at Joints

• Planes of motion:

  • Uniaxial: Movement in one plane (e.g., hinge)

  • Biaxial: Movement in two planes (e.g., saddle, ellipsoid)

  • Multiaxial: Movement in all axes (e.g., ball-and-socket)

• Types of motion:

  • Flexion/extension/hyperextension: Decrease/increase angle at joint

  • Lateral/medial excursion: Side-to-side movement (jaw)

  • Pronation/supination: Rotation of forearm

  • Rotation: Turning around axis

  • Dorsiflexion/plantar flexion: Upward/downward movement of foot

  • Circumduction: Circular movement

  • Protraction/retraction: Anterior/posterior movement (jaw, scapula)

  • Elevation/depression: Upward/downward movement (shoulders, jaw)

  • Inversion/eversion: Turning sole of foot inward/outward

Lyme Disease

• Type of infection: Bacterial (caused by Borrelia burgdorferi)

• Transmission: Spread by the bite of infected ticks (usually deer ticks)

Table: Types of Synovial Joints and Examples

Joint Type	Movement	Example
Plane	Gliding	Intercarpal joints
Hinge	Uniaxial (flexion/extension)	Elbow, knee
Pivot	Uniaxial (rotation)	Atlas/axis, proximal radioulnar joint
Condyloid (Ellipsoid)	Biaxial (flexion/extension, abduction/adduction)	Wrist
Saddle	Biaxial	Thumb (1st carpometacarpal joint)
Ball-and-socket	Multiaxial	Shoulder, hip

Additional info:

• For bone growth, the process of endochondral ossification involves the replacement of hyaline cartilage with bone tissue, which is essential for the formation of long bones.

• Vitamin D is crucial for calcium absorption in the intestines, which is necessary for healthy bone mineralization.